Anionic polymeric stabilizers for oil-in-water emulsions

ABSTRACT

A terpolymer mixture having emulsifying and emulsion stabilizing properties comprising a mixture of (1) a water soluble vinyl monomer, (2) a water insoluble vinyl monomer having 12 to 30 carbon atoms and (3) a polymerizable vinyl monomer containing acid groups. The terpolymer may be used in combination with oil and water to form stable oil-in-water emulsions or in enhanced oil recovery procedures.

REFERENCE TO RELATED APPLICATIONS

This is a continuation of Ser. No. 214,791 filed Jul. 5, 1988, nowabandoned which is a continuation-in-part of application Ser. No.026,583, filed Mar. 17, 1987, now abandoned, which was a divisional ofapplication Ser. No. 706,229 filed Feb. 27, 1985, now abandoned.

BACKGROUND OF THE INVENTION

The present invention is directed to novel terpolymers emulsionstabilizers for oil-in-water emulsions. In particular, the presentinvention is directed to the use of terpolymers of water soluble vinylmonomers and water insoluble vinyl monomers having long chain alkylgroups and polymerizable vinyl monomers containing acid groups useful inthe formation of stable oil-in-water emulsions. The emulsion stabilizersof the present invention have specific utility in cleaning oilcontaminated vessels, oil spill management, pipeline transportation ofheavy crude oil drag reduction in pipeline pumping of oil, and enhancedoil recovery by chemical flooding.

The use of ordinary surfactants or emulsifiers to produce stableoil-in-water emulsions has been attempted in the prior art. Ordinarysurfactants, generally, are compounds which have a low molecular weight(e.g. less than 30 carbon atoms) and contain hydrophilic (water-loving)and lipophilic (oil-loving) groups. When a mixture of oil and water ismechanically sheared in the presence of these types of surfactants, thesurfactants distribute themselves at the oil-water interface as thedroplets of oil are formed thus facilitating the formation of anoil-in-water emulsion. Because of the faster mobility of the lowmolecular weight surfactants, they are quite effective in forming aninitial emulsion of the oil and water. However, when the mechanicalshear is removed and the emulsion is allowed to stand for some time(i.e. a few hours, days) most emulsions made from this type ofsurfactant tend to separate. The reason attributed to the separation isthat the mobility of the surfactants are such that they move in and outof the surface of the oil droplets leaving some surface area of the oildroplets exposed. Accordingly, when two oil droplets collide at anexposed site, coalescence of the droplets occurs. As time goes on,larger and larger droplets of oil are formed resulting in the separationof the oil phase from the water phase. Accordingly, to stabilize theoil-in-water emulsions the use of a material which is not mobile wouldbe highly desirable.

In U.S. Pat. No. 4,311,832 to Gutnick et. al., a naturally occurringlong chained material suitable for emulsions stabilization ofoil-in-water emulsions is disclosed. The material is identified as"EMULSAN". The emulsion stabilizer properties of "EMULSAN" arise fromits unique structure which consists of a large molecular weight moleculecontaining both hydrophilic and lipophilic groups. The large molecularweight of the emulsan molecule is such that once the molecules havepositioned themselves at the oil water interface they tend to stay thereresulting in a highly stable emulsion. While emulsions produced by theuse of "EMULSAN" have exhibited high stability they are produced bybiotechnological procedures which are relatively inflexible.Accordingly, the "EMULSAN" product cannot be easily modified because ofits dependence on bacteria to make the product. Therefore, the use of asynthetic high molecular weight material as a emulsion stabilizer wouldbe preferable because it could be modified or produced by variousprocedures giving the resulting molecule various properties notpossessed by the biotechnological product.

Synthetic polymeric materials having emulsifying properties can be foundin the prior art. For example, U.S. Pat. No. 2,816,882 to Schillerdiscloses polymeric surface active agents comprising copolymers ofacrylamide or methacrylamide and acrylic or methacrylic acid esters of ahigher molecular weight saturated aliphatic alcohol having at least 8carbon atoms. In addition, U.S. Pat. Nos. 3,691,124 and 4,464,508disclosed copolymers of acrylamides for use in water-in-oil emulsionstabilization. Finally, U.S. Pat. Nos. 4,463,151 and 4,463,152 discloseacrylamide acrylate copolymers as viscosification agents. Applicant'sinvention is directed to terpolymers containing water soluble vinylmonomers and water insoluble vinyl monomers having long chain alkylgroups (C=12-20) and vinyl monomers containing acid groups and their useas emulsifiers and emulsion stabilizers for oil-in-water emulsions.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a novel polymericemulsion stabilizer composition capable of producing stable oil-in-wateremulsion.

It is a further object of the present invention to provide a novelpolymer emulsion stabilizer composition suitable for use with lowmolecular weight surfactants.

It is another object of the present invention to provide a novel stableoil-in-water emulsion.

It is still another object of the present invention to provide a polymerpossessing emulsifying and emulsion stabilizing properties for use inproduction of a stable oil-in-water emulsion.

For purposes of this invention the term oil is understood to mean a widerange of materials. For example, the term is intended to include mineraloil, vegetable oil, animal oils, etc. Preferably, the present inventionis directed to oils that are naturally occurring hydrocarbons and inparticular normal crude oil, heavy crude oil and viscous refineryproducts.

In order to better clarify the terms "heavy crude" and "viscous refineryproducts," initially, it should be understood that there is nouniversally accepted, clear-cut definition for heavy crudes. In thecontext of the present invention, "heavy" and "viscous" will beconsidered synonymous. While low API gravity, i.e., high density, doesnot necessarily coincide with high viscosity, these characteristics arealmost always correlated. Similar statements apply to what is referredto as "viscous refinery products," which for purposes of the presentinvention should be taken to include any viscous, usually high-density,liquid or semi-solid material remaining following the refining process.Vacuum resid and asphalt are primary examples of such materials. Thefollowing characteristics usually are considered typical of thesehydrocarbons:

1. Low API gravity, generally at or below 20°. This is the mostfrequently used criterion, both because it is easily measured andbecause 20° crude roughly corresponds to the lower limit recoverablewith conventional production techniques.

2. Viscosities in the range of 10² to 10⁶ centipoises (cp) or evenhigher in some cases.

3. High metal contents. For example, heavy crudes often have nickel andvanadium contents as high as 500 ppm. Resids can sometimes be evenhigher in metals.

4. High sulfur content, e.g., 3 weight percent or more, especially forvacuum bottoms.

5. High asphaltene content.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description that follows and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practicing the invention. The object andadvantages of the invention may be realized and obtained by means of theinstrumentalities and combinations particularly pointed out in theappended claims.

To achieve the foregoing and other objects in accordance with thepurpose of the present invention as embodied and broadly describedherein, the emulsion stabilizer and/or emulsifying terpolymer of thepresent invention comprises a mixture of (1) a water soluble vinylmonomer, (2) a water insoluble vinyl monomer having an alkyl chaincontaining about 12 to 30 carbon atoms and (3) a polymerizable vinylmonomer containing an acid group or its water soluble salt such as Na, Kor NH₄.

In another aspect of the present invention, the method of producing astable oil-in-water emulsion comprising mixing water, oil and aterpolymer comprising a mixture of (1) a water soluble vinyl monomer,(2) a water insoluble vinyl monomer having an alkyl chain containingabout 12 to 30 carbon atoms and (3) a polymerizable vinyl monomercontaining an acid group or its water soluble salt such as Na, K or NH₄.

In still another aspect of the present invention, a method is providedfor cleaning oil contaminated vessels comprising mixing the terpolymerof the present invention with water to dissolve the terpolymer in thewater and applying the water-terpolymer mixture to the surface of theoil contaminated vessel to remove the oil from the surface of thevessel. The oil removed from the surface of the vessel mixes with theterpolymer-water mixture to form a stable oil-in-water emulsion whichcan be readily removed from the vessel.

In a further aspect of the present invention, the stable oil-in-wateremulsion of the present invention comprises oil, water and a terpolymercomprising a mixture of (1) a water soluble vinyl monomer, (2) a waterinsoluble vinyl monomer and (3) a polymerizable vinyl monomer containingacid groups or its water soluble salt such as Na, K or NH₄.

In a preferred embodiment of the present invention, the stableoil-in-water emulsion of the present invention includes a low molecularweight surfactant. The term low molecular weight surfactant refers toany conventional surfactant known to anyone having ordinary skill in theart. Illustrative of these known surfactants are petroleum sulphonates.

The terpolymers of the present invention produce oil-in-water emulsionsthat are extremely stable and relatively insensitive to brine content.Accordingly, unlike other oil-in-water emulsions utilizing low molecularweight materials, the emulsions of the present invention remains stablefor extremely long periods of time (e.g., weeks, months). In addition,in contrast to the oil-in-water emulsions of U.S. Pat. No. 4,311,832,the polymeric material used in the oil-in-water emulsion of the presentinvention can be changed quite easily (i.e., changing the startingmaterials). Accordingly, the synthetic emulsifier and emulsionstabilizer of the present invention may be tailored to possess theproperties desired. Moreover, the anionic characteristics of theseterpolymers will enhance the solubility of these polymers in water.

DETAILED DESCRIPTION OF THE INVENTION

The novel water soluble terpolymers of the present invention used informing the stable oil-in-water emulsions of the present inventioncomprise a mixture of (1) a water soluble vinyl monomer, (2) a waterinsoluble vinyl monomer having an alkyl chain containing about 12 to 30carbon atoms and (3) a polymerizable vinyl monomer having an acid groupor its water soluble salt (e.g., Na, K, Ca or NH₄). Preferably, theterpolymers of the present invention comprise a mixture of (1)acrylamide or methacrylamide, (2) long chain (C₁₂ -C₂₂) alkyl acrylateor methacrylate esters, and (3) an ethylenically unsaturated carboxylicacid.

The production of the terpolymer of the present invention employs amonomeric mixture of three monomers each in certain proportions. Thefirst being a monomeric water soluble vinyl compound. The second being amonomeric water insoluble vinyl compound having an alkyl chaincontaining about 12 to 30 carbon atoms. The third being a polymerizablevinyl monomer containing an acid group or its water soluble salt.Typically, the proportions of each monomer should be 10 to 50 weight %acid containing vinyl monomer, 0.1 to 20% water insoluble vinyl monomerand 30 to 85 weight % water soluble vinyl monomer. Preferably, theproportions of each monomer in the mixture should be 20 to 35 weight %acid containing vinyl monomer, 1 to 15 weight % water insoluble monomerand 50 to 75 weight % water soluble monomer.

The water soluble vinyl monomer can be chosen from the group consistingof acrylamide and methacrylamide, vinyl methyl ether, N-methylacrylamide, N,N-dimethylacrylamide, N-methacryloylglycinamide, vinylpyrrolidone, and N-vinyloxazolidone.

The water insoluble vinyl monomer can be chosen from the groupconsisting of long chain (C₁₂ to C₃₀) alkyl acrylate esters, long-chainN alkyl acrylamides or methacrylamides, long chain vinyl esters and longchain vinyl ethers. Preferably, the water insoluble monomer is longchain alkyl acrylate ester having the formula: ##STR1## wherein R₂ is analkyl group containing 12 to 30 carbon atoms, preferably 12 to 22 carbonatoms and R₁ is hydrogen or methyl. Typical monomers falling within thisgeneral class are, lauryl methacrylate, stearyl methacrylate and others.Typical monomers of the long-chain N-alkyl acrylamide class includeN-octadecyl acrylamide, N-octadecyl methacrylamide, and N,N-dioctylacrylamide.

The polymerizable vinyl monomer may be selected from ethylenicallyunsaturated carboxylic acid such as acrylic and methacrylic acid,sulfonic acids such as AMPS (2-acrylamido-2-methyl propane sulfonicacid) or styrene sulfonic acid and vinyl phosphates such as vinylphosphonic acid or their water soluble salts.

Most preferably, the ethylenically unsaturated carboxylic acid are used.Typical examples of these types of materials include acrylic acid,methacrylic acid, fumaric acid, itaconic acid, citraconic acid, aconiticacid, etc.

Preferably, the terpolymer of the present invention is made bypolymerization in an inert diluent having some solubilizing action onone or more of the monomeric ingredients but substantially none on theresultant polymer. Polymerization in mass may be employed but is notpreferred because of the difficulty in working up the solid polymericmasses obtained. Polymerization in an aqueous medium containing awater-soluble free radical catalyst peroxygen is useful, the productbeing obtained either as a granular precipitate or as a highly swollengel, either of which may be used directly or are easily furthersubdivided and dried. Most preferably, polymerization takes place in anorganic liquid which is solvent for the monomers but a non-solvent forthe polymer, or in a mixture of such solvents, in the presence of asolvent-soluble catalyst because the product is usually obtained as avery fine friable and often fluffy precipitate which, after solventremoval, seldom required grinding or other further treatment before use.Solvents for the latter method include benzene, xylene, Tetralin,hexane, petane, carbon tetrachloride, methyl chloride, ethyl chloride,methyl ethyl ketone, acetone, acetonitrile, ethylene dichloride, andmixtures of these and other solvents.

In addition, other known polymerization techniques such as inverseemulsion polymerization as disclosed in U.S. Pat. Nos. 3,284,393 toVanderhoff et al and 3,624,019 to Anderson and Frisque may be utilizedin the production of the terpolymers of the present invention. Thedisclosure of these patents is herein incorporated by reference.

Polymerization in the diluent medium is carried out in the presence of afree radical catalyst in a closed vessel in an inert atmosphere andother autogenous pressure or artificially-induced pressure or in an openvessel under reflux at atmospheric pressure. Temperature of thepolymerization may be varied from 0° C. to 100° C., depending to a largedegree on the molecular weight desired in the polymer and the initiatorchosen. Polymerization under reflux at 50° C. to 90° C. underatmospheric pressure using a free radical catalyst is generallyeffective in bringing a polymer yield of 75% to 100% in less than 10hours. Suitable catalysts include peroxygen compounds such as sodium,potassium and ammonium persulfates, carpylyl peroxide, benzoyl peroxide,hydrogen peroxide, pelargonyl peroxide, cumene hydroperoxides, tertiarybutyl diperphthalate, tertiary butyl perbenzoate, sodium peracetate,sodium percarbonate, and the like as well as 2,2-azobisisobutyronitrile(AIBN). Other catalysts utilizable are the so-called "redox" type ofcatalyst and the heavy-metal activated catalyst systems.

EMULSION FORMATION

The stable oil-in-water emulsions of the present invention are producedby a method comprising placing a terpolymer, oil and water in acontainer and mixing the components to form the stable emulsion. Due tothe extreme stability of the oil-in-water emulsions of the presentinvention, they are useful in oil spill management, pipelinetransportation of normal or heavy crude, and cleaning of oilcontaminated vessels. The polymeric material used in the presentinvention is characterized as both an emulsifier and emulsion stabilizerbecause it not only has the ability to emulsify the oil and water but tostabilize the oil and water once the emulsion has been formed.

In a preferred embodiment of the present invention, the terpolymer ispredissolved in the water prior to mixing with the oil. This procedurefacilitates dissolution of the terpolymer and decreases the timerequired to mix the components to form the oil-in-water emulsion.

This procedure is especially preferred in cleaning oil contaminatedvessels. For example, the terpolymer of the present invention, includinglow molecular weight surfactant if present, is mixed with water todissolve the terpolymer and surfactant. This mixture is then appliedusually with pressure (e.g., spray apparatus or hose) to the surface ofthe oil contaminated vessel to remove the oil and form a stableoil-in-water emulsion. The resulting stable oil-in-water emulsion can beremoved from the vessel by conventional means known in the art leaving asubstantially clean surface.

The length of time required to mix the components to form the resultingstable emulsion of the present invention is not critical. However,mixing should be performed for a time sufficient to insure uniformdispersion of the terpolymer throughout the solution in order that theterpolymer molecules move to the oil water interface. For example, inthe case of forming the stable emulsion with a predissolved terpolymer,mixing for 20 minutes would be sufficient.

Most preferably, the oil-in-water emulsion of the present inventioncontains a conventional low molecular weight surfactant to facilitatethe formation of the emulsion. The use of a low molecular weightsurfactant reduces substantially the time required to form the emulsionbecause the conventional surfactant is highly mobile. Therefore, duringmixing of the components, the conventional surfactant distributes itselfrapidly at the oil-in-water interface as the droplets of oil are formed.The polymeric emulsifier and emulsion stabilizer then distributes itselfabout the oil droplets to stabilize the already formed oil-in-wateremulsion. Any conventional low molecular weight surfactant compatiblewith the polymeric emulsifier and emulsion stabilizer may be utilized inthe practice of this embodiment of the present invention. For example,the petroleum or alkylaryl sulphonate surfactants such as thosedescribed in Recent Advances in Surfactant Flooding, Mattax C. C.,Proceeding World Petroleum Congress, 1983, 11 (3) Pg. 205 (1084), hereinincorporated by reference, may be utilized in the practice of thepresent invention.

In a preferred embodiment of the present invention, the oil-in-wateremulsion comprises up to about 80 weight % oil, 0.1 to 5 weight %terpolymer, and the remainder being water. Most preferably, theoil-in-water emulsion comprises up to about 70 weight % oil, 0.1-3weight % terpolymer, and remainder being water.

In an especially preferred embodiment of the present invention, a lowmolecular weight surfactant is used in combination with the terpolymerand the sum of both terpolymer and low molecular weight surfactant inthe emulsion is between about from 0.1 to 5 weight % and preferably 0.1to 3 weight %.

In addition to forming stable oil-in-water emulsions, the terpolymers ofthe present invention may also be utilized in enhanced oil recoveryprocedures heretofore reserved for aqueous solution of polyacrylamide,polysaccharides and ethylene polyoxides. The terpolymer of the presentinvention when placed in water improves the sweep efficiency of thewater thereby increasing the amount of oil recovery. For a more detaileddescription of the use of polymers in enhanced oil recovery, see Latil,Enhanced Oil Recovery, Gulf Publishing Co., 1980 herein incorporated byreference.

The oil-in-water emulsions of the present invention possess extremelygood stability due to the emulsion stabilization properties of theterpolymer of the present invention. The use of a combination of aconventional surfactant and a polymeric surfactant of the presentinvention provides an extremely good result. The conventional emulsifierfacilitates the formation of emulsions, while the polymeric surfactantstabilizes them.

The foregoing description of the preferred embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and obviously manymodifications and variations are possible in light of the abovedisclosure. The embodiments were chosen and described in order toexplain best the principle of the invention and its practicalapplications to thereby enable others skilled in the art to best utilizethe invention in its various embodiments and with various modificationsas are suited to the particular use contemplated. It is intended thatthe invention be defined by claims appended hereto.

What is claimed as the invention is:
 1. A water soluble terpolymerhaving emulsifying and emulsion stabilizing properties consistingessentially of the polymerized mixture of (1) 30 to 85 weight percent ofa water soluble vinyl monomer selected from the group consisting ofacrylamide, methacrylamide, vinyl methyl ether, N-methyl acrylamide,N,N-dimethylacrylamide, N-methacryloylglycinamide, vinyl pyrrolidone,and N-vinyloxazolidone, (2) 0.1 to 20 weight percent of a waterinsoluble vinyl monomer having an alkyl chain containing about 12 to 30carbon atoms selected from the group consisting of alkyl acrylateesters, vinyl esters and vinyl ethers, and (3) 10 to 50 weight percentof a polymerizable vinyl monomer containing an acid group or its watersoluble salt selected from the group consisting of ethylenicallyunsaturated carboxylic acids, sulfonic acids, vinyl phosphonic acids,and the sodium, lithium, calcium or ammonium water soluble salts ofthese carboxylic acids, sulfonic acids and vinyl phosphonic acids. 2.The terpolymer of claim 1 wherein said water insoluble vinyl monomer hasan alkyl chain containing 12 to 22 carbon atoms.
 3. The terpolymer ofclaim 2 wherein said water soluble vinyl monomer is selected fromacrylamide and methacrylamide.